add interprocedural Java example

Reviewed By: cristianoc

Differential Revision: D2744378

fb-gh-sync-id: 0ef57a7

examples/README

@@ -23,12 +23,14 @@ Contents
   Make sure that you have the Android SDK 22 installed and up to date, and in
   particular the "Android SDK Build-tools" and "Android Support Repository".
 
-- ios_hello/: a sample iOS app. Try this example by running
-  infer -- xcodebuild -target HelloWorldApp -configuration Debug -sdk iphonesimulator
-
 - c_hello/: a sample make-based C project. Try this example by running
   infer -- make
 
+- ios_hello/: a sample iOS app. Try this example by running
+  infer -- xcodebuild -target HelloWorldApp -configuration Debug -sdk iphonesimulator
+
+- java_hello/: a sample Java project. Try this example by running
+  infer -- javac Pointers.java Resources.java Hello.java
 
 Note
 ----

examples/java_hello/Hello.java

@@ -0,0 +1,64 @@
+/*
+* Copyright (c) 2015 - present Facebook, Inc.
+* All rights reserved.
+*
+* This source code is licensed under the BSD style license found in the
+* LICENSE file in the root directory of this source tree. An additional grant
+* of patent rights can be found in the PATENTS file in the same directory.
+*/
+
+package hello;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Random;
+
+class Hello {
+
+  void doesNotCauseNPE() {
+    Pointers.A a = Pointers.mayReturnNull(10);
+    a.method();
+  }
+
+  void mayCauseNPE() {
+    Random rng = new Random();
+    Pointers.A a = Pointers.mayReturnNull(rng.nextInt());
+    // FIXME: should check for null before calling method()
+    a.method();
+  }
+
+  void mayLeakResource() throws IOException {
+    OutputStream stream = Resources.allocateResource();
+    if (stream == null) {
+      return;
+    }
+
+    try {
+      stream.write(12);
+    } finally {
+      // FIXME: should close the stream
+    }
+  }
+
+  /**
+   * This method should be rewritten with nested try { ... } finally {
+   * ... } statements, or the possible exception raised by fis.close()
+   * should be swallowed.
+   */
+  void twoResources() throws IOException {
+    FileInputStream fis = null;
+    FileOutputStream fos = null;
+    try {
+      fis = new FileInputStream(new File("whatever.txt"));
+      fos = new FileOutputStream(new File("everwhat.txt"));
+      fos.write(fis.read());
+    } finally {
+      if (fis != null) { fis.close(); }
+      if (fos != null) { fos.close(); }
+    }
+  }
+
+}

examples/java_hello/Pointers.java

@@ -0,0 +1,26 @@
+/*
+* Copyright (c) 2015 - present Facebook, Inc.
+* All rights reserved.
+*
+* This source code is licensed under the BSD style license found in the
+* LICENSE file in the root directory of this source tree. An additional grant
+* of patent rights can be found in the PATENTS file in the same directory.
+*/
+
+package hello;
+
+public class Pointers {
+
+  public static class A {
+    public void method() {
+    }
+  }
+
+  public static A mayReturnNull(int i) {
+    if (i > 0) {
+      return new A();
+    }
+    return null;
+  }
+
+}

examples/java_hello/Resources.java

@@ -0,0 +1,27 @@
+/*
+* Copyright (c) 2015 - present Facebook, Inc.
+* All rights reserved.
+*
+* This source code is licensed under the BSD style license found in the
+* LICENSE file in the root directory of this source tree. An additional grant
+* of patent rights can be found in the PATENTS file in the same directory.
+*/
+
+package hello;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+public class Resources {
+
+  public static FileOutputStream allocateResource() {
+    try {
+      File file = new File("foo.txt");
+      return new FileOutputStream(file);
+    } catch (IOException e) {
+      return null;
+    }
+  }
+
+}